array comparison vs SQL join - php

Question

I have two, big, 2 dimensional arrays (pulled from some xml data) one (A list) is ~1000 items containing 5 fields the other (B list) is dinamically between 10.000-12.000 items containing 5 fields.
My idea was to compare EACH id key of list A against EACH id key of list B and on "true" compose a new array of combined fields, or just fields from array A if no match.
I used nested foreach loops and ended up with millions of iterations taking long time to process. needless to say...not a solution.
The form of this two structures and my needed result reminded me straight away of a sql join.
The questions are:
1.) Should i try sql or nested foreach might not be the best php way?
2.) Will a relational query be much faster than the iterations?
EDIT:
I pull data only periodically from an xml file (in a separate process) which contains 10+ fields for each node. Than i store the 5 fields i need in a CSV file to later compare with table A that i pull out from a mysql database. basically much like catalog update of attributes with fresh feed.
I'm affraid the original idea of storing into CSV was an error and i should just save the feed updates into a database too.
EDIT 2
The array list B look like this
Array
(
[0] => Array
(
[code] => HTS541010A9E680
[name] => HDD Mobile HGST Travelstar 5K100 (2.5", 1TB, 8MB, SATA III-600)
[price] => 385.21
[avail] => 0
[retail] => asbis
)
...
...
while the A list is similar in all but the 'code' field which is the only one useful for comparison
Array
(
[0] => Array
(
[code] => ASD-HTS541010A
[name] => HDD Mobile HGST Travelstar 5K100 (2.5", 1TB, 8MB, SATA III-600)
[price] => 385.21
[avail] => 0
[retail] => asbis
)
As you can see each feed will have universal code BUT some different random data as prefix or suffix so in each loop i have to do a couple of operations on the string to stripos or compare it to feeds id for a match or close match.
Pseudo code:
$mylist = loadfromDB();
$whslist = loadfromCSV();
foreach ($mylist as $myl) {
foreach ($whslist as $whl){
if ((stripos(code_a,code_b) OR (code_b,code_a) !== false)){
...
}
elseif (stripos(substr(strstr(code_a,'-'),1),code_b) !== false) {
...
}
elseif (stripos( substr(code_a,0,-5);) == !false ){
...
}
}
}

Answer 1

Using SQL will be faster because most SQL engines are optimized for joins, and your method is a brute-force method. However, inserting all that data to MySQL tables is quite a heavy task, so it's still not the best solution.
I suggest you do the join in PHP - but use a smarter algorithm. Start by sorting the two arrays by the field you want to match. Iterate both sorted arrays together - use two iterators(or pointers or indices or whatever) - lets say a iterates over A and b over B. On each iteration of the loop, compare the comparison field of the elements pointed by the a and b. If a's is smaller - advance a. If b's is smaller - advance b. If a's is equal to b's - you have a match, which you should store in a new list, and then advance both a and b(assuming the relation is one-to-one - if it's one-to-many you only advance the many iterator, and if it's many-to-many you need a bit more complex solution).